Alternator and regulator control system

ABSTRACT

An alternator and regulator control system includes diodes connected to the output windings of the alternator to pass unidirectional current pulses and to cause blocking of current when voltage in the output winding reverse biases the diodes. This blockage of current produces a high reverse voltage pulse in the output winding which is then delivered to the field winding of the alternator through electronic switch means to cause excitation of the alternator to develop high power output in the stator windings of the alternator. The electronic switch is a thyristor and forms part of a feedback circuit which is controlled by a voltage regulator that controls the output voltage of the alternator.

United States Patent Riff [ 51 June 27, 1972 ALTERNATOR AND REGULATORCONTROL SYSTEM James A. Riff, Chicago, Ill.

Motorola, Inc., Franklin Park, 111.

Aug. 5, 1971 Inventor:

Assignee:

Filed:

Appl. No.:

References Cited UNITED STATES PATENTS 7/1966 Shimwell et a1. ..322/9lUX l/l967 Rath ..322/75 X I] VOLTAGE I 3,544,881 12/1970 Raver et a1..322/28 X Primary Examiner-Lewis H. Myers Assistant Examiner-H.Huberfeld [57] ABSTRACT An alternator and regulator control systemincludes diodes connected to the output windings of the alternator topass unidirectional current pulses and to cause blocking of current whenvoltage in the output winding reverse biases the diodes. This blockageof current produces a high reverse voltage pulse in the output windingwhich is then delivered to the field winding of the alternator throughelectronic switch means to cause excitation of the alternator to develophigh power output in the stator windings of the alternator. Theelectronic switch is a thyristor and forms part of a feedback circuitwhich is controlled by a voltage regulator that controls the outputvoltage of the alternator.

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ALTERNATOR AND REGULATOR CONTROL SYSTEM BACKGROUND OF THE INVENTION Thisinvention relates generally to dynamoelectric machines and moreparticularly to an alternator and regulator control circuit of the typeused in automotive electrical systems.

Alternators used in the electrical charging systems of automobiles arewell known in the art and have always been considered a very efficientmachine for charging the automobile battery and operating variouselectrical equipment as compared to the old DC generator type of system.The alternator produces an alternating current voltage at the outputthereof which is rectified through a plurality of diodes, generally in afull wave configuration, to provide the necessary DC voltage to theelectrical components and battery charging system of the automobile. Thealternator system is considered superior to the DC generator in thatcharging current is obtained even when the engine is running at slowspeed. Although the alternator charging system is considered relativelyefiicient, it has nevertheless some energy losses as a result of rapidturn off of diode rectifiers at the output. The rapid turn ofi thediodes causes a high reverse voltage pulse to be developed at the outputwinding of the alternator as a result of the reduced current in thereverse direction of the diodes.

In the prior art the rotating field of the alternator is excited by a DCcurrent from the battery or alternator output, which is generallycontrolled by means of a voltage regulator. While this is a relativelycommon and straight forward method of exciting the rotating field of thealternator it requires external power to initiate start up operation ofthe alternator because of the relatively low levels of residualmagnetism retained in the alternator components. This can be overcome byinitially operating the alternator at high speeds. However, in somecases in the prior art small permanent magnets are put into thealternator to provide the magnetic field necessary for self start up of.the alternator. Also, the power output level of prior art alternators issubstantially constant over a given range of engine speed and load.Forexample, a typical output may be about 40 amperes when the field isexcited by the battery source and with an armature speed of betweenabout 2,000 and 8,000 rpm. This example is with a full wave rectifierarrangement at the output of the alternator. However, if the output isprovided with a half wave rectifier arrangement, the output of thealternator will be increased at the higher rpm's but reduced at thelower rpm's. In any event, because of the field being fed by the batteryor charging supply. The power output of the alternator is substantiallylimited for a given machine design and construction.

SUMMARY OF THE INVENTION Accordingly, it is an object of this inventionto provide an improved alternator and regulator control system that willproduce much more power output from the alternator for a given machinedesign and construction than can be presently obtained by conventionalmethods.

Yet another object of this invention is to provide an alternator andregulator control system wherein the excitation for the field isobtained by the reverse voltage pulses which occur upon turnoff of theoutput diodes of the alternator system.

Still another object of this invention is to provide an improvedalternator and regulator control system which allows an alternator tooperate more efficiently by utilizing the reverse voltage pulsesgenerated inherently in the machine to energize the rotating fieldthereof.

Briefly, the alternator and regulator control system includes the outputwindings of an alternator structure which are connected in WYEconfiguration. The field winding of the alternator is arranged toreceive pulses of direct current to develop a magnetic field which, inturn, generates the output of the alternator. The pulses of directcurrent are converted either through a full wave bridge rectifier orhalf wave rectifier through a thyristor such as silicon controlledrectifier or other device in response to a switching circuit whichcontrols the passage of high reverse voltage pulses developed as aresult of rapid turn off of the output diodes. This high reverse voltagecondition occurs each time current ceases to flow through a given outputwinding by reverse biasing of the associated diode. The feedback of thehigh reverse voltage pulses to the field winding is obtained through aswitching circuit controlled in response to a voltage regulator. Thehigh reverse voltage pulses are many times greater in voltage value thanis obtained by the battery charging system at the alternator output thatit induced a much higher voltage into the rotating field. This increasedvoltage, which is obtained from within the alternator itself, willgreatly increase the output of the alternator far beyond that which canbe obtained by present conventional methods. The switching circuit whichmay form part of the voltage regulator will operate in the conventionalmanner but will switch the high reverse voltage pulses rather than theconventional battery voltage. For example, when the switching circuit isin the open condition, no feedback of high reverse voltage pulses occursand the output of the alternator is reduced. On the other hand, uponsensing a demand for more power the switching circuit is closed, byenergization of an electronic switching device, to provide a currentpath for the reverse voltage pulses. One very significant advantage ofthe present invention is that the increased power which is obtained isat the higher rpm s of the rotor which, because of an associated fan,will produce sufficient cooling air to fiow over the alternator housingand cool the same.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of oneform of alternator and regulator control system of this inventionwherein a rotary transformer is associated with the alternator;

FIG. 2 is a voltage regulator which can be used in the circuit of FIG.1;

FIG. 3 is a series of waveforms which represent the output of thealternator and regulator control system of FIG. 1;

FIG. 4 is an alternate form of alternator and regulator control systemconstructed in accordance with this invention; and

FIG. 5 illustrates the several power curves obtained both from full waveand half wave alternator outputs of conventional design and also showsthe marked improvement of alternator output when using the high reversevoltage pulses in accordance with this invention.

DESCRIPTION OF THE ILLUSTRATES EMBODIMENTS Referring now to FIG. I thereis seen an alternator and regulator control system designated generallyby reference numeral 10. The alternator is illustrated as having anoutput winding 12, which is generally the stator of the alternator, anda rotating field winding 14. The field winding 14 is energized toprovide a magnetic field which, in turn, induces an alternating currentvoltage in the output windings 12. In the illustrated embodiment, theoutput windings 12 are connected in WYE configuration with windings 12a,12b and 12c connected together at a common circuit point 13 which, inturn, is here illustrated at the positive output terminal of the system.

Output diodes 16a, 16b and 16c are connected to the windings 12a, 12band 120, respectively, to rectify the alternating current voltageinduced in these windings to produce a direct current voltage across theoutput terminals 18 and 20. It will be noted that this is three phasehalf wave rectification where only three diodes are used rather than theusual six diode full wave configuration. When the cathode electrodes ofdiodes 16a, 16b and 160 are negative the alternating current voltage isdelivered to terminals 18 and 20 in the form of pulsating DC. However,at the end of each negative half cycle, the diodes are instantlyrendered nonconductive in the usual manner. This rapid nonconduction ofthe diodes causes a reverse voltage condition to exist in the statorwindings 12a, 12b and in successive sequence in accordance with theirsequence of energization. Heretofore, this reverse voltage pulse orkickback voltage was dissipated within the system and this energy waslost. In accordance with the general concepts of this invention, thesereverse voltage pulses are fed back to the field winding 14 to energizethe alternator system. 7

For a better understanding of the operation of the alternator andregulator control system of FIG. 1, reference is now made to FIG. 3which illustrates the half wave pulses 22 which occur at the output ofwinding 12b, and the half wave pulses 24 which occur at the outputwinding-12c. I-Ialf wave pulses 26 which occur at the output winding 12aare also illustrated, but the reverse voltage pulses that are producedby these pulses are not used for field excitation. At the bottom of eachpulse, a broken line indicates the high voltage short time durationreverse voltage kickback pulse 22a, 24a and 26a for the associatedpulses 22, 24 and 26, respectively. Pulses 22b and 24b correspond to thereverse voltage pulses and are delivered to a rotary transformer 32 ateach end thereof from windings 12b and 12c in time relation so thatcurrent passes alternately in one direction and then in the otherdirection through the primary winding 32a. Also, since the reversepulses are obtained from across two windings 12b and 12c the net voltageis twice that otherwise obtained and the small amount of residualmagnetism remaining in the system is then sufficient to initiateoperation of the alternator.

The primary winding 32a is connected to a voltage regulator 40 to havethe circuit thereof open and close in response to a switching mechanismindicated by 42 connected between the lines 44 and 46. When the switch42 is open, no current passes through the primary winding 32a and nopulses are trans former coupled across the rotary transformer 32.However, upon sensing the output voltage at terminals 18 and 20, thisbeing accomplished over lines 48 and 50, switch 42 closes and pulses ofcurrent then pass through the primary winding. Pulses of current whichare transformer coupled into the rotary secondary winding 32b arerectified to produce a DC voltage by a plurality of diodes 33 which formthe bridge rectifier circuit 34. The output of the bridge circuit 34 isfiltered by a capacitor 36 and applied to the field winding 14 as a DCor a pulsating DC current. The rotary secondary winding 32b, the bridgecircuit 34, and capacitor 36 and field winding 14 are all mounted on acommon shaft for rotation therewith thus eliminating the need forbrushes or other mechanical connections to the field winding.

The voltage regulator 40 may take any convenient form, which will sensevariations in output voltage across terminals 18 and 20 and operativelyenergize and tie-energize the switching device 42. The switching device42 may be any relatively fast acting electronically or electricallycontrolled switching device.

Referring now to FIG. 2, a voltage regulator switching circuit 40Aillustrates one such form of voltage regulator which can be used in thecircuit of FIG. 1. The regulator 40A has input lines 48a and 50acorresponding to lines 48 and 50 of FIG. 1 for receiving the energizingvoltage. A reverse bias protection diode 51 is connected across theselines and a voltage divider network including resistors 52 and 53together with a thermistor S4 and capacitor 56 form the basictemperature compensation network for the regulator circuit. Variationsin ambient temperature are thus compensated by changes in resistancevalue of the thermistor S4. The center tap 55 of the voltage dividernetwork is then applied to the base electrode of a transistor 57 througha zener diode 58 which provides a reference voltage for regulation. Acontrol current is developed across a biasing resistor 59 between thebase and emitter electrodes of transistor 56 while the collector emitterelectrodes are shunted by a capacitor 60 which absorbs any spikes orincreased voltage transients that occur in the circuit. The output oftransistor 57 is connected to the gate electrode of a triac 62 through adiode 63. Although a trial is shown in this embodiment it will beunderstood that any device of the applied to the gate electrode thereof.A capacitor 64 is connected between the gate electrode of the triac andthe line 44a to filter extraneous signals to prevent inadvertentconduction of the triac. When voltage at output terminals 18 and 20 isgreater than the desired output voltage, the zener diode 58 will conductwhich, in turn, renders transistor 57 conductive to reverse bias thegate electrode of the triac 62 and maintain it in an open circuit ornonconductive condition. However, when voltage across terminals 18 and20 decreases below a predetermined voltage value, zener diode 58 becomesnonconductive and transistor 57 similarly becomes nonconductive. Thisallows the pulses applied to the triac to pass through the gateelectrode thereof more freely and through capacitor 64 to render thetriac conductive and perform its switching function and allow thereverse voltage pulses to be applied to the rotary transformer 32.

Referring now to FIG. 4 there is seen an alternate form of an alternatorand regulator control system constructed in accordance with thisinvention, which is designated generallyv by reference numeral 70. Thecontrol system includes the output windings 72 of an alternator, shownhere connected in WYE configuration with the center common terminal 73thereof connected to ground potential. A field winding 74 of thealternator is located in close proximity to the output winding 72 todevelop a magnetic field and induce alternating current voltage in theoutput windings. The output windings 72a, 72b and 720 are connected tooutput diodes 76a, 76b and 760, respectively, to deliver half wavepulses of direct current to the positive output terminal 77. The outputterminals 77 and 78 are of opposite polarity than that shown in FIG. 1,it being understood that mere reversal of connection of the diodes orother semiconductor components will change the polarity of the outputvoltage. When diodes 76a, 76b and 76c are rendered nonconductive, theyproduce a high voltage reverse voltage pulse in their associated windingwhich is then delivered to the field winding 74 through a feedbackcircuit 80. Here the feedback circuit 80 consists merely of a siliconcontrolled rectifier 82 which has its anode connected to the outputwindings 72 and its cathode connected to the field winding 74. The gateelectrode of silicon controlled rectifier 84 is controlled by a voltageregulator circuit designated generally by 83. A voltage developingresistor 84 is connected between the gate and cathode of siliconcontrolled rectifier 82 and a turn on resistor 86 is connected to thegate of silicon controlled rectifier 82 and to an ignition terminal 87.Therefore, upon turning on the ignition switch of an automobile, theregulator system is placed in readiness for operation when the engineturns the alternator rotor. To provide a slight magnetic field forinitial operation, the field winding 74 is connected to the ignitionterminal 87 through a resistor 88 which is of relatively high resistancevalue, but which allows sufficient current flow through the fieldwinding to produce a slight magnetic field to initiate start up of thecharging system. The alternator field 74 is shunted by a diode 89 whichserves to prevent recirculating currents from developing high voltageswith the field winding.

The alternator and regulator circuit system of FIG. 4 operates insubstantially the same manner as that disclosed with regard to FIG. 1 inthat current through the field winding is developed as a result of thereverse voltage pulses developed in the output windings by rapidnonconduction of the output diodes 76a, 76b and 760. These reversevoltage pulses may have a magnitude of about 4 times greater than thatof the normal half wave pulses applied to the output terminal and thusprovides a very efficient output voltage from the alternator system.

An indicating lamp 96 receives operating potential via a pair of diodes91 and 92 connected to the output windings 72a and 72b, respectively.This applies two of the three output pulses to line 93 which, in turn,has the terminal 94 arranged for connection to the indicating lamp 96which is located within the automobile. The indicating lamp 96 has theother end thereof connected to battery potential and, when the ignitionswitch is closed, no current passes through the diodes 91 and 92 and thelamp is energized from the battery voltage through a load resistor 97.However, when output voltage is obtained from the alternator, line 93becomes positive to about the same voltage value as that of the batteryand a no voltage condition exists across the indicating lamp 96 toextinguish it. Only the two diodes 91 and 92 are needed to de-energizethe lamp 96 because of the increased voltage obtained from the statorwindings 72a and 72b. Prior to the development of this invention threediodes were needed for this function.

The current control transistor 99 is connected to the gate electrode ofsilicon controlled rectifier 82 to control its operation. A transistor100 is operated as a zener diode by having its collector electrode tiedback to its base electrode and the base emitter junction connected inseries with the base electrode of a transistor 101. Transistor 101functions as a temperature compensating unit. Transistor 99 is thenrendered operative to short circuit the gate cathode circuit of siliconcontrolled rectifier 82 to disable the rectifier. On the other hand,when bias voltage is removed from resistors 102 and 103, transistor 99is rendered inoperative, which, in turn will cause conduction of siliconcontrolled rectifier 82 via its voltage dropping resistor 84. Thevoltage setting at the output terminals 77 and 78 can be adjusted by avariable voltage divider network comprising a resistor 106 and apotentiometer 107 which is connected to the transistor 100 which isconnected to act as a zener diode. The potentiometer 107 is shunted by afilter capacitor 109 which eliminates extraneous signals from beingapplied through the zener diode.

Silicon controlled rectifier 82 operates with the same function as thetriac 62 of FIG. 2, and the switch means 42 of FIG. 1. It allows thereverse voltage pulses to be applied to the field winding 74 only whenin the conductive state and blocks such pulses when renderednonconductive by the voltage regulator circuit 83.

For a better understanding of the improved power output obtained by thisinvention reference is now made to the graph shown in FIG. 5 which showsoutput amperes versus alternator rpm. Here the curve 120 shows thetypical full wave output of a conventional alternator regulatorarrangement. With the average usable range of alternator rpm between3,000 and 8,000 rpm the output is substantially constant at about 40amperes for this type of alternator. When a half wave output arrangementis used within low rpm range, it will produce a reduced power output,but at the higher rpm range the power output will be increased as shownby the curve 121. In both cases the field was fed an excitation voltagefrom the battery or charging system. When using the arrangement of thepresent invention on the very same alternator the output is so greatlyincreased that excessive amounts of current can be obtained, this beingshown by the partial solid and partial broken line curve 122. To preventdamage to the alternator a ohm resistor was inserted into the field lineto limit the voltage applied thereto. The output power obtained with theIQ ohm resistor is shown by the curve 123 which reaches 100 amperes fora machine that previously reached only 40 amperes on full wave and 65amperes on halfwave.

What has been described is a simple and efficient alternator andregulator control system which utilizes the reverse voltage pulsesgenerated in the output windings as a result of rapid nonconduction ofthe output diodes to produce a control cur rent for the field winding ofthe alternator.

I claim:

1. An alternator and regulator control system comprising in combination,output windings for developing an alternating current output voltagehaving first and second polarities, a field winding positioned adjacentsaid output windings for developing a magnetic field to induce thealternating current output voltage into said output windings, rectifiermeans connected to said output voltage to rectify said alternatingcurrent output voltage, said rectifier means being highly conductivewith said output voltage of the first polarity to pass unidirectionalcurrent and being highly nonconductive with said output voltage of thesecond polarity to block current, and the transition from conduction tononconduction of said rectifier means producing a reverse voltage pulsein said output windings, and feedback means connected between saidoutput windings and said field winding to utilize said reverse voltagepulses for energizing of said field winding.

2. The alternator and regulator control system of claim I wherein saidfeedback means includes a rotary transformer for receiving said reversevoltage pulses, said rotary transformer including a fixed primarywinding for said reverse voltage pulses and a rotating secondary windingrotatable with said field winding, and a second rectifier meansconnected between said rotating secondary winding and said field windingto deliver direct current pulses to said field winding to produce amagnetic field therein.

3. The alternator and regulator control system of claim 2 wherein saidsecond rectifier means is a bridge rectifier circuit.

4. The alternator and regulator control system of claim 1 wherein saidfeedback means includes a silicon controlled rectifier having loadelectrodes and a control electrode, said load electrodes connectedbetween said output winding and said field winding for passing saidreverse voltage pulses to produce a magnetic field within said fieldwinding, and regulator means for controlling the gate electrode of saidsilicon controlled rectifier to render the same conductive andnonconductive in response to demands for output voltage from the saidoutput windings.

5. The alternator and regulator control system of claim 4 wherein saidsilicon controlled rectifier has its anode connected to said outputwindings and its cathode connected to said field winding.

6. An alternator and regulator control system comprising in combination,a first winding means for developing an alternating current voltageoutput, a second winding means positioned adjacent said first windingmeans for developing a magnetic field to induce the alternating currentoutput voltage into said first winding means, means connected to saidfirst winding means to convert the alternating current output voltage toa direct current voltage by passing current of one polarity and blockingcurrent of the other polarity such that the transition from a currentpassing condition to a current blocking condition causing reversevoltage pulses to be developed in said first winding means, feedbackmeans for delivering said reverse voltage pulses from said first windingmeans to said second winding means to develop the magnetic fieldtherein, and regulator circuit means having terminals connected to saidmeans for converting said alternating current output voltage to saiddirect current voltage to sense the value thereof and produce a controlsignal, said regulator circuit means including switch means responsiveto said control signal to switchably connect said reverse voltage pulsesfrom said first winding means to said second winding means.

7. The alternator and regulator control system of claim 6 wherein saidswitch means of said regulator circuit means is a silicon controlledrectifier having the anode thereof connected to said means forconverting said alternating current output voltage to said directcurrent voltage and the cathode thereof connected to said second windingmeans.

8. The alternator and regulator control system of claim 6 wherein saidswitch means is a triac which allows pulses of current to pass in bothdirections, and further including a rotary transformer having the fixedprimary winding thereof connected in series with said triac to receivesaid reverse voltage pulses and a rotary secondary winding thereofconnected to said second winding means through a bridge rectifiercircuit.

9. The alternator and regulator control system of claim 6 furtherincluding a light indicating circuit consisting of a lamp having oneterminal connected to a battery supply of the control system, and twodiodes connected to said first winding means and the other terminal ofsaid lamp to provide a counteracting voltage thereto and extinguish thelamp.

1. An alternator and regulator control system comprising in combination,output windings for developing an alternating current output voltagehaving first and second polarities, a field winding positioned adjacentsaid output windings for developing a magnetic field to induce thealternating current output voltage into said output windings, rectifiermeans connected to said output voltage to rectify said alternatingcurrent output voltage, said rectifier means being highly conductivewith said output voltage of the first polarity to pass unidirectionalcurrent and being highly nonconductive with said output voltage of thesecond polarity to block current, and the transition from conduction tononconduction of said rectifier means producing a reverse voltage pulsein said output windings, and feedback means connected between saidoutput windings and said field winding to utilize said reverse voltagepulses for energizing of said field winding.
 2. The alternator andregulator control system of claim 1 wherein said feedback means includesa rotary transformer for receiving said reverse voltage pulses, saidrotary transformer including a fixed primary winding for said reversevoltage pulses and a rotating secondary winding rotatable with saidfield winding, and a second rectifier means connected between saidrotating secondary winding and said field winding to deliver directcurrent pulses to said field winding to produce a magnetic fieldtherein.
 3. The alternator and regulator control system of claim 2wherein said second rectifier means is a bridge rectifier circuit. 4.The alternator and regulator control system of claim 1 wherein saidfeedback means includes a silicon controlled rectifier having loadelectrodes and a control electrode, said load electrodes connectedbetween said output winding and said field winding for passing saidreverse voltage pulses to produce a magnetic field within said fieldwinding, and regulator means for controlling the gate electrode of saidsilicon controlled rectifier to render the same conductive andnonconductive in response to demands for output voltage from the saidoutput windings.
 5. The alternator and regulator control system of claim4 wherein said silicon controlled rectifier has its anode connected tosaid output windings and its cathode connected to said field winding. 6.An alternator and regulator control system comprising in combination, afirst winding means for developing an alternating current voltageoutput, a second winding means positioned adjacent said first windingmeans for developing a magnetic field to induce the alternating currentoutput voltage into said first winding means, means connected to saidfirst winding means to convert the alternating current output voltage toa direct current voltage by passing current of one polarity and blockingcurrent of the other polarity such that the transition from a currentpassing condition to a current blocking condition causing reversevoltage pulses to be developed in said first winding means, feedbackmeans for delivering said reverse voltage pulses from said first windingmeans to said second winding means to develop the magnetic fieldtherein, and regulator circuit means having terminals connected to saidmeans for converting said alternating current output voltage to saiddirect current voltage to sense the value thereof and produce a controlsignal, said regulator circuit means including switch means responsiveto said control signal to switchably connect said reverse voltage pulsesfrom said first winding means to said second winding means.
 7. Thealternator and regulator control system of claim 6 wherein said switchmeans of said regulator circuit means is a silicon controlled rectifierhaving the anode thereof connected to said means for converting saidalternating current output voltage to said direct current voltage andthe cathode thereof connected to said second winding means.
 8. Thealternator and regulator control system of claim 6 wherein said switchmeans is a triac which allows pulses of current to pass in bothdirections, and further including a rotary transformer having the fixedprimary winding thereof connected in series with said triac to receivesaid reverse voltage pulses and a rotary secondary winding thereofconnected to said second winding means through a bridge rectifiercircuit.
 9. The alternator and regulator control system of claim 6further including a light indicating circuit consisting of a lamp havingone terminal connected to a battery supply of the control system, andtwo diodes connected to said first winding means and the other terminalof said lamp to provide a counteracting voltage thereto and extinguishthe lamp.